1. Field of the Invention
The present invention relates to a thin-plate supporting container for storing thin plates such as semiconductor wafers, storage disks, or liquid crystal glass substrates, which is adapted to be used for storage, for transportation, or in the manufacturing process.
2. Description of the Related Art
A thin-plate supporting container for storage or transportation with thin plates such as semiconductor wafers stored therein is generally known. Such a thin-plate supporting container is disclosed in Japanese Unexamined Patent Application Publication No. 2002-122382. The thin-plate supporting container in this publication will be described referring to FIG. 2.
A thin-plate supporting container 1 mainly includes a container body 2 and a lid unit 3 for closing an opening on top of the container body 2. In the container body 2, there is provided a thin-plate supporting unit 6 for supporting a plurality of semiconductor wafer 4 stored therein at regular intervals. The thin-plate supporting unit 6 includes plate supporting strips 7 for holding the peripheral portions of the semiconductor wafers 4 when the container body 2 is place sideways (the state in which the semiconductor wafers 4 are oriented in the horizontal direction), and V-shaped grooves (not shown) provided on the inner sides of the respective plate supporting strips 7 for supporting the semiconductor wafer 4 at the center portion of the respective plate supporting strips 7 by allowing the semiconductor wafers 4 to fall into the groove bottom when the container body 2 is placed vertically.
On the inner surface of the lid unit 3, there is provided thin-plate holding units 8 for pressing and supporting the semiconductor wafers 4 supported by the thin-plate supporting unit 6 from the lid unit 3 side. The thin-plate holding unit 8 includes V-shaped grooves (not shown) for fitting and supporting the semiconductor wafers 4 by the number corresponding to the number of stored semiconductor wafers 4. The V-shaped grooves have their center positions aligned with the center positions of the V-shaped grooves of the thin-plate supporting unit 6 and formed symmetrically. Accordingly, the V-shaped grooves hold the respective semiconductor wafers 4 at predetermined positions.
Generally, in this thin-plate supporting container 1, the semiconductor wafers 4 are automatically taken out and put by the semiconductor wafer transporting device in a state in which the container body 2 is place sideways, and then the lid unit 3 is attached thereon.
In the case of the thin-plate supporting container 1 as describe above, the semiconductor wafers 4 are displaced form the V-shaped grooves of the thin-plate supporting unit 6 and are placed on the respective plate supporting strips 7 when the container body 2 is placed sideways. Therefore, the semiconductor wafers 4 are in the state of being shifted downward from the groove bottoms of the V-shaped grooves of the thin-plate supporting unit 6.
In contrast, since the V-shaped grooves on the thin-plate holding units 8 on the lid unit 3 side are at the positions aligned with the V-shaped grooves of the thin-plate supporting unit 6 of the container body 2, the semiconductor wafers 4 may shift from the centers of the V-shaped grooves of the thin-plate holding units 8. Therefore, there is a problem in that when attaching the lid unit 3 in a state in which the container body 2 is placed sideways, the V-shaped grooves of the thin-plate holding units 8 cannot be fitted to the peripheral portions of the semiconductor wafers 4 smoothly.
Also, in a state in which the thin-plate supporting container 1 is washed, and hence little dust or dirt is attached on the lower surfaces of the V-shaped grooves, the semiconductor wafers 4 can hardly be run smoothly and may be caught by the lower surface. In this case, since the semiconductor wafer 4 is oriented obliquely, there arises a problem in that the V-shaped grooves of the thin-plate holding units 8 cannot be fitted smoothly on the peripheral portions of the semiconductor wafers 4, or automatic operation in taking the semiconductor wafers 4 in and out by a transporting device may not work properly.
Also, there is a case in that ridges 9A, 9B, and 9C for supporting the semiconductor wafer 4 are formed as the plate supporting strip of the thin-plate supporting unit as shown in FIG. 3. In this case, only one of the ridges 9A, 9B, and 9C is provided. If the position to provide the ridge 9 is too front (like the ridge 9A), the ridge 9A has to be formed inwardly (the position which is significantly extended leftward in the drawing) of a front portion 7A of the plate supporting strip 7, and hence it is difficult to reinforce. Consequently, the plate supporting strip 7 may be deflected and hence the semiconductor wafer 4 may be displaced to a large extent. On the other hand, when the ridge 9 is formed at the position too inside (like the ridge 9C), most part of the weight of the semiconductor wafer 4 is exerted on the ridge 9C, and hence the weight of the semiconductor wafer 4 which is exerted to the lower surface of a V-shaped groove 7B is reduced. Accordingly, a frictional force of the semiconductor wafer 4 placed on the ridge 9C increases, and a force that the semiconductor wafer 4, which is placed on the lower surface of the V-shaped groove 7B of the thin-plate supporting unit 6, slides along the lower surface by its own weight (a force to press the semiconductor wafer 4 forward) is decreased. Accordingly, since the semiconductor wafer 4 is caught by the lower surface and hence is oriented obliquely, there may arise problems such that the V-shaped groove on the thin-plate holding unit 8 cannot fit smoothly on the peripheral portion of the semiconductor wafer 4, or the automatic operation in taking the semiconductor wafer 4 in and out by the transporting device may not work properly.
In addition, when the thin-plate holding units 8 provided on the inner side of the lid unit 3 press and support the plurality of semiconductor wafers 4 stored in the container body 2 simultaneously, the thin-plate holding units 8 receive resilient forces from the respective semiconductor wafers 4. Although the thin-plate holding units 8 are supported by the lid unit 3, since the center portion of the lid unit 3 is low in strength, there is a problem in that the force to press and support the plurality of semiconductor wafers 4 by the thin-plate holding units 8 is also weak at the center portion.